variable costs,fixed cost, total cost

Project Description:

bridget ashton isgetting ready to open a small restaurant. she is on a tight budget and must choose between the following long-distance phone plans:
plan a :pay 1 0 cents per minute of long-distance calling'.
plan b :pay a fixed monthly fee of $15 for up to 240 long-distance minutes, and 8 cents per minute thereafter (if she uses fewer than 240 minutes in a month in any month, she still pays $15 for the month).
plan c: pay a fixed monthly fee of $22 for up to 510 long-distance minutes and 5 cents per minute thereafter (if she uses fewer than 510 minutes, she still pays $22 for the month).